The field of the invention is hydrocarbons and the present invention is particularly concerned with the preparation of cyclododecatri-(1,5,9)-enes by catalytically trimerizing butadiene using a catalyst of a titanium halide and an alkyl aluminum halide in the presence of hydrocarbons or halogenated hydrocarbons.
The state of the art of catalytic trimerization of butadienes to cyclododecatrienes may be ascertained by reference to U.S. Pat. No. 2,964,574 and German Pat. No. 1,112,069, the disclosures of which are incorporated herein.
The cyclododecatri-(1,5,9)-enes are recovered by distillation and vinylcyclohexene and cyclooctadi-(1,5)-ene are obtained as distilled by-products and higher butadiene polymers as non-distilled by-products. The polymers initially dissolved in the mixture of reaction cause an appreciable increase in the viscosity of the solution and thereby the butadiene absorption is decreased and difficult processing of the mixture of the reaction occurs. The process is also known to work in the presence of complexing additives or semi-polar compounds and in the presence of slight amounts of water, for the purpose of decreasing the formation of higher polymers as disclosed in U.S. Pat. Nos. 3,076,045 and 3,149,173 and British Pat. No. 1,102,833, the disclosures of which are incorporated herein.
Dibenzylbenzenes useful in the present invention are disclosed in U.S. Pat. No. 2,954,412, the disclosure of which is incorporated herein.
Hydrocarbons or halogenated hydrocarbons such as benzene, toluene, xylene, chlorobenzene, heptane, cyclohexane, isooctane, even cyclododecatriene itself, especially however, benzene, are used as diluents in the trimerization. These low-boiling point diluents after completion of reaction are first distilled off and only then, and in another distillation batch, follows the higher-boiling-point cyclododecatriene and the other oligomers, vinylcyclohexene and cyclooctadiene. The catalyst remains in the residue and therefore cannot be used again in the next batch or in a continuous process on account of the required recovery.